Field of the Invention
The present invention relates to a display device having a configuration of inspecting elements.
Description of the Background Art
In usual, in a liquid crystal display device, liquid crystal is sealed into a space formed of: two electrode substrates laminated to each other by a sealant; and the sealant. Transparent electrodes are formed on the respective electrode substrates. Moreover, the sealant is formed on a periphery of a display region for displaying a video. Hereinafter, a region on the periphery of the display region will also be referred to as a “peripheral region”. The peripheral region is a region that surrounds the display region when viewed as a plane (XY plane) from the above. The peripheral region is also a frame region of the liquid crystal display device.
Moreover, a drive system of the liquid crystal display device includes an active matrix type and a passive matrix type. An active matrix-type liquid crystal display device has a TFT array substrate in which thin film transistors as switching elements are formed in a matrix. In the liquid crystal display device, the TFT array substrate and a counter substrate are laminated to each other through the sealant. The liquid crystal is sealed between the TFT array substrate and the counter substrate.
On the display region of the TFT array substrate, there are provided gate wires, source wires, pixel electrodes and the like. By a gate signal that propagate through the gate wires, a state of the TFT as the switching element is set to an ON state or an OFF state. A source signal that propagates through the source wires is supplied to the pixel electrodes through the TFTs.
Then, when the source signal is supplied to each of the pixel electrodes, a display voltage, which corresponds to the source signal, is applied between the counter electrode and the pixel electrode. In this way, the liquid crystal is driven. The gate signal that propagate through the gate wires and the source signal that propagates through the source wires are supplied from driver ICs.
Hence, on the peripheral region, there are formed wires for connecting the driver ICs and the gate wires and the source wires to each other. Moreover, the sealant and common wires are formed on the peripheral region. A common signal for giving a common potential to the counter substrate is propagated through the common wires.
In order to confirm whether or not the liquid crystal display device operates normally, a configuration (hereinafter, also referred to as an “inspection configuration”) for performing a variety of inspections is usually provided in the liquid crystal display device concerned. In JP 11-338376 A, a liquid crystal display panel (device) provided with the inspection configuration is disclosed. Moreover, in JP 11-338376 A, a technology (hereinafter, also referred to as “Related Art A”) using the inspection configuration is disclosed.
In Related Art A, inspection signals are transmitted from inspection terminals to a plurality of scanning lines (gate wires) and a plurality of data lines (source wires). Then, a plurality of inspection TFTs provided between the inspection terminals and the plurality of scanning lines and between the inspection terminals and the plurality of data lines are controlled, whereby the variety of inspections are performed. In Related Art A, there is disclosed a configuration capable of inspection by several inspection signals by collectively controlling the plurality of inspection TFTs.
In Related Art A, when the liquid crystal display panel (liquid crystal display device) is driven, a constant-level voltage for turning the inspection TFTs to an OFF state is applied to the inspection TFTs concerned.
In general, as a period while the same level-voltage is being applied to the inspection switching elements (inspection TFTs) is longer, a change of a threshold value of the inspection switching elements is increased. That is to say, as the period while the same level-voltage is being applied to the inspection switching elements is longer, a state of the inspection switching elements turns to an ON state in some case by an unexpected voltage from an outside.
In this case, there is a problem that a malfunction that quality of a video decreases occurs since unnecessary currents (leak currents) flow from the inspection switching elements in the ON state to the switching elements for displaying the video.
Therefore, in order to prevent such a malfunction described above, it is required to suppress prolongation of the period while the same level-voltage is applied to the inspection switching elements no matter whether the period concerned may be a period while a display device such as the liquid crystal display device is displaying a video or may be a period while the display device is not displaying the video.